Secondary battery with protective circuit board and secondary protective element

ABSTRACT

A secondary battery with a protective circuit module including a rechargeable bare cell having a first electrode and a second electrode and a protective circuit board having a protective circuit for the rechargeable bare cell. A conductive bonding layer is located on the protective circuit board and a secondary protective element assembly is attached to the protective circuit board by the conductive bonding layer. A first lead plate electrically connects the secondary protective element assembly to the first electrode, and a second lead plate electrically connects the protective circuit board to the second electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2006-0115245, filed on Nov. 21, 2006, the entirecontent of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a secondary battery with a protectivecircuit module.

2. Description of the Prior Art

Generally, as portable wireless devices such as video cameras, cellularphones, portable computers, and the like have become more lightweightand increasingly developed, research has been conducted on secondarybatteries used for driving such devices. Secondary batteries arerechargeable and can be compact, yet have a high capacity. Conventionalsecondary batteries may be, for example, nickel-cadmium batteries,nickel-hydrogen batteries, nickel-zinc batteries, lithium secondarybatteries, and the like. Lithium secondary batteries are widely usedamong other reasons, due to their high operating voltage and high energydensity per weight.

Secondary batteries may be classified into cylinder type batteries usinga cylindrical aluminum can, rectangular type batteries using arectangular aluminum can, and pouch type batteries housed in a thinpouch case.

In rectangular secondary batteries, a bare cell is formed by stacking ananode plate, a cathode plate and a separator and winding them to form anelectrode assembly. The electrode assembly is then inserted into arectangular metal can, and an open portion of the rectangular can issealed by a cap plate to form a bare cell. Furthermore, an insulatedelectrode terminal is provided on the cap plate, wherein the electrodeterminal forms one electrode of the secondary battery, and the cap plateand the can form the other electrode.

A protective circuit module (PCM) including a secondary protectiveelement such as a positive temperature coefficient (PTC) element and aprotective circuit board may be mounted on the upper part of the barecell as a safety device for the secondary battery.

The PTC element functions as a conductor at normal temperature, and butceases to function as a conductor when electric resistance is increasedin proportion to increased surrounding temperature or is otherwisesubjected to relatively high temperatures. Typically, the PTC element isconnected to the protective circuit board by spot welding.

In conventional secondary batteries, after an electrically conductivenickel (Ni) plate is attached to a protective circuit board, a PTCelement is coupled to the electrically conductive plate by spot welding.In order to couple the PTC element to the protective circuit board,equipment, such as a welding jig, is needed, and a relativelycomplicated connection operation is required. Further, since theelectrically conductive nickel plate is attached to the protectivecircuit board by surface mount technology (SMT), the production cost ofthe secondary battery is relatively high. Additionally, due to therelatively high temperature applied to the PTC element by welding duringassembly, the functionality of the PTC element may deteriorate.

SUMMARY OF THE INVENTION

A secondary battery with a protective circuit module is providedincluding a rechargeable bare cell having a first electrode and a secondelectrode and a protective circuit board having a protective circuit forthe rechargeable bare cell. A conductive bonding layer is located on theprotective circuit board and a secondary protective element assembly isattached to the protective circuit board by the conductive bondinglayer. A first lead plate electrically connects the secondary protectiveelement assembly to the first electrode, and a second lead plateelectrically connects the protective circuit board to the secondelectrode. As used herein, a lead plate is an electrically conductiveplate that may comprise any electrically conductive material.

The conductive bonding layer may be a thermal bonding layer or may besolder. The rechargeable bare cell may be rectangular having a firstside (or lateral side) and a second side, the rechargeable bare cellfurther comprising an insulated electrode terminal on the first side,and wherein the protective circuit board is on the second side.

The secondary protective element assembly may include a connecting platebonded to the protective circuit board by the conductive bonding layer.More specifically, the connecting plate may include a first connectingportion in contact with the conductive bonding layer, a coupling portionextending from the first connecting portion, and a second connectingportion substantially parallel to the first connecting portion. Thefirst connecting portion may have a plurality of through holes allowingthe conductive bonding layer to penetrate therethrough. The protectivecircuit board may include a plurality of protective circuitssurface-mounted on a printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects according to exemplary embodiments of thepresent invention will be apparent from the following detaileddescription and the accompanying drawings, in which:

FIG. 1 is an exploded perspective detail view of a protective circuitmodule according to an exemplary embodiment of the present invention.

FIG. 2 is a side view of the protective circuit module of FIG. 1.

FIG. 3 is an exploded perspective detail view of a protective circuitmodule according to another exemplary embodiment of the presentinvention.

FIG. 4 is a side view of the protective circuit module of FIG. 3.

FIG. 5 is an exploded perspective view illustrating a secondary batteryto which protective circuit module according to an exemplary embodimentof the present invention is attached.

FIG. 6 is a side view of the secondary battery of FIG. 5.

DETAILED DESCRIPTION

Referring to FIG. 5, a secondary battery 1 according to an exemplaryembodiment of the present invention includes a bare cell 10 and aprotective circuit module comprising a protective circuit board 20, aconductive bonding layer 30, a secondary protective element 40, aconnecting plate 150, and first and second lead plates 60, 70. Anexternal terminal 22 for electrical connection of the secondary batteryto external electronic equipment, such as a mobile telephone, may bemounted on the protective circuit board 20.

Referring now to FIGS. 1 and 2, the protective circuit board 20comprises a protective circuit for protecting the bare cell 10 fromover-charging and over-discharging, the protective circuit board 20adapted to receive various protective elements mounted thereon.

The conductive bonding layer 30, which may comprise a thermal bondinglayer, is located on a surface of the protective circuit board 20, andattaches a secondary protective element assembly including the secondaryprotective element 40 to the protective circuit of the protectivecircuit board 20, as will be described in more detail below. In oneexemplary embodiment, the conductive bonding layer is softened byheating and placed in contact with a surface of the secondary protectiveelement assembly. The conductive bonding layer is then cooled so itbonds to and becomes integral with the secondary protective elementassembly. In particular, the conductive bonding layer may be, in oneexemplary embodiment, formed by solder which provides excellentelectrical conductivity and relatively short melting and hardeningtimes.

As noted above, the conductive bonding layer 30 may be located betweenthe secondary protective element 40 and the protective circuit board 20.In one exemplary embodiment, the secondary protective element 40 is apositive temperature coefficient (PTC) element commonly used as a safetyfeature in secondary batteries. The PTC element functions as a conductorwhen at an operating temperature, and ceases to function when electricresistance is increased in proportion to the increased surroundingtemperature, or when the temperature of the PTC element is otherwiseincreased above a threshold temperature. Once the temperature of the PTCelement has returned to an operating temperature, the PTC element againfunctions as a conductor.

The secondary protective element 40 may be electrically connected to theconnecting plate 50 by a connecting member. In one exemplary embodiment,the connecting plate 50 comprises a first connecting portion 51 attachedto the conductive bonding layer 30 and having a width substantiallyidentical to or slightly narrower than a width of the conductive bondinglayer 30. However, the width of the first connecting portion 51 is notlimited thereto.

The connecting plate 50 may further comprise a coupling portion 52extending at substantially a right angle between the first connectingportion 51 and a second connecting portion 53 parallel to the firstconnecting portion 51. As such, the second connecting portion 53 isspaced from the first coupling portion, and therefore, from theconductive bonding layer and protective circuit board, by the couplingportion 52. In one exemplary embodiment, the first connecting portion51, the coupling portion 52 and the second connecting portion 53 aregenerally planar and may comprise nickel (Ni).

The first lead plate 60 connects the secondary protective element 40with a first electrode of the bare cell 10. Accordingly, the protectivecircuit board 20 and the bare cell 10 are connected through thesecondary protective element 40. Similarly, the second lead plate 70connects a second electrode of the bare cell 10 to the protectivecircuit board 20.

With reference now to FIGS. 3 and 4, an exemplary embodiment of aprotective circuit module comprises a plurality of through holes 151 ain a first connecting portion 151 of a connecting plate 150, alsoincluding a coupling portion 152 and a second connecting portion 153.Accordingly, when the connecting plate 150 is attached to the protectivecircuit board 20 using the conductive bonding layer 30, a portion of theconductive bonding layer 30 penetrates the through holes 151 a. Thebonding material which penetrates the through holes 151 a is hardened toform a reinforcement protrusion 154 to reinforce the attachment of theprotective circuit board to the connecting portion 151. Accordingly, theprotective circuit board 20 is more securely coupled to the connectingplate 150, resulting in the secondary protective element 40 being moresecurely coupled to the protective circuit board 20.

The protective circuit module according to the exemplary embodimentsdescribed above may also be incorporated, for example, into atransverse-type pack secondary battery or a transverse-type inner pack.

With reference now to FIGS. 5 and 6, the bare cell 10 is generallyrectangular having an insulated electrode terminal 12 mounted on a firstside. In one exemplary embodiment, a gasket 14 is located between thebare cell 10 and the insulated electrode terminal 12. A protectivecircuit 24 may be mounted on the protective circuit board 20. Theprotective circuit board 20 may be positioned along a second side of thebare cell 10 such that the conductive bonding layer 30 is located alongan interior-facing surface. The external terminals 22 are mounted on anexterior-facing surface of the protective circuit board 20 opposite theconductive bonding layer 30, and insulating members 15, 16 are securedto longitudinal sides of the bare cell 10. In one exemplary embodiment,the insulating members 15, 16 may be, for example, insulating tape orthe like.

According to an exemplary construction of a secondary battery of thepresent invention, the secondary protective element may be fixed to theprotective circuit board merely by the bonding force of the conductivebonding layer 30 between the connecting plate 50 and the protectivecircuit board. Accordingly, the secondary protective element can beattached to the protective circuit board without spot welding equipment,such as a welding jig, simplifying the manufacturing process.Furthermore, high temperatures produced by welding are not necessaryduring the attachment process, allowing the secondary protective elementto be attached without being affected by such high temperatures, andthus potentially deteriorating the quality of the secondary protectiveelement.

Although exemplary embodiments of the present invention have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications thereof are possible withoutdeparting from the scope and spirit of the present invention as definedin the following claims.

What is claimed is:
 1. A secondary battery with a protective circuitmodule comprising: a rechargeable bare cell having a first electrode anda second electrode; an electrode terminal protruding from therechargeable bare cell; a protective circuit board comprising aprotective circuit for the rechargeable bare cell; a conductive bondinglayer on the protective circuit board; a secondary protective elementassembly comprising a connecting plate bonded to the protective circuitboard by the conductive bonding layer; a first lead plate electricallyconnecting the secondary protective element assembly to the firstelectrode; a second lead plate directly contacting the electrodeterminal and the protective circuit board to electrically connect theprotective circuit board to the second electrode; and an insulatingmember secured to a longitudinal side of the rechargeable bare cell,wherein the insulating member is both between a portion of the firstlead plate and the rechargeable bare cell and between a portion of thesecond lead plate and the rechargeable bare cell, wherein the connectingplate comprises a first connecting portion in contact with theconductive bonding layer, a coupling portion extending from the firstconnecting portion, and a second connecting portion substantiallyparallel to the first connecting portion, wherein the first connectingportion comprises a plurality of through holes allowing the conductivebonding layer to penetrate therethrough and a portion of the conductivebonding layer forming a reinforcement protrusion on a side of the firstconnecting portion opposite the protective circuit board.
 2. Thesecondary battery as claimed in claim 1, wherein the conductive bondinglayer comprises a thermal bonding layer.
 3. The secondary battery asclaimed in claim 1, wherein the conductive bonding layer comprisessolder.
 4. The secondary battery as claimed in claim 1, wherein therechargeable bare cell is rectangular comprising a lateral side, whereinthe electrode terminal is on the lateral side, and wherein theprotective circuit board is on the longitudinal side.
 5. The secondarybattery as claimed in claim 1, wherein the connecting plate comprises afirst connecting portion in contact with the conductive bonding layer.6. The secondary battery as claimed in claim 1, wherein the connectingplate comprises nickel.
 7. The secondary battery as claimed in claim 1,wherein the secondary protective element assembly comprises a positivetemperature coefficient element.
 8. The secondary battery as claimed inclaim 1, wherein the protective circuit board comprises a plurality ofprotective circuits surface-mounted on a printed circuit board.